30 THE MECHANISTIC THEORY OF LIFE 



perfectly clear working hypothesis that the 

 peculiar phenomena of life are due to the 

 play of the physical and chemical environ 

 ment on intra-protoplasmic mechanisms which 

 have been evolved through the influence of 

 natural selection acting for ages. If this 

 theory is correct, the aim of biology is to 

 unravel the mechanism ; and biology itself is 

 nothing but a branch of physics and chemistry, 

 which we may, if we like, distinguish as bio 

 physics and bio-chemistry. The alternative 

 hypothesis of the vitalists has been shown to 

 be unproved, unintelligible, and practically 

 useless as a scientific working hypothesis. 



In the next lecture the mechanistic theory 

 itself will be examined. 



